Two short months ago, the Kansas City Chiefs and San Francisco 49ers each entered Week 1 with an over/under of 8.5 wins. They've taken wildly different paths since then, providing bookends to the first half of the 2018 season.

The Chiefs are 8-1 against the spread and have gone from 30-1 to win the Super Bowl to +450 at the SuperBook at the Westgate Las Vegas, while the 49ers are one loss from cashing an under bet.

Scoring is up, but are there more over bets cashing this season? Which teams' Super Bowl odds have changed the most since Week 1?

Here are some midseason betting takeaways for an exciting 2018 season:

Note: Win totals and futures odds for the 2018 season are from the SuperBook at the Westgate Las Vegas. Historical win totals and futures odds are sourced from Sports Odds History.

Chiefs are one win away from the over

With a victory over the Arizona Cardinals this Sunday, Kansas City (8-1 record, O/U 8.5 wins) would become the first NFL team this season to hit the over for regular-season wins. Patrick Mahomes and Co. are 16.5-point home favorites.

If the Chiefs win nine or more games -- at this point a near certainty -- they will extend their "over streak" to six consecutive seasons, longest in the NFL. The New England Patriots (7-2, O/U 11) can match that streak if they finish with at least 12 wins. (The Patriots went over their win total in the five seasons before this one and haven't gone under since 2009. They pushed in 2012.)

Since 2002, the teams that most exceeded their over/unders were the 2004 Pittsburgh Steelers (15-1, O/U 7.5) and 2004 San Diego Chargers (12-4, O/U 4.5), both by 7.5 wins. Even if the Chiefs run the table to finish 15-1, the best they can do is go over their total by 6.5 wins.

The Rams are competing with high expectations

Several teams are poised to follow the Chiefs in hitting the over. The Miami Dolphins (5-4, O/U 6.5) need just two more wins. Seven teams need three more wins, including the Chicago Bears (5-3, O/U 7.5), whose five-year "under streak" is the longest in the NFL, and the Los Angeles Rams (8-1, O/U 10).

How to bet NFL Week 10

The Rams started the season 10-1 to win the Super Bowl, moved to 7-1 before Week 2, +450 before Week 3 and as high as 2-1 before Week 4, rocketing past the Patriots to become Super Bowl favorites. They peaked at +160 before losing to the New Orleans Saints last Sunday, and are now the favorites at +250 at Westgate.

Those Super Bowl odds are indicative of the Rams' high expectations. Prior to last week, they had been favored by at least 6.5 points in every game this season. That makes covering a tall task, and Los Angeles is a modest 4-4-1 ATS. Kansas City, meanwhile, has been an underdog three times and only twice favored by more than a touchdown; the Chiefs are a league-best 8-1 ATS.

But the Rams have wreaked betting havoc in other ways, turning Green Bay's Aaron Rodgers and Seattle's Russell Wilson into the biggest single-game underdogs of their respective careers -- at least at certain points leading up to those games. (The Rams-Packers line closed at Rams -7.5, ultimately making Rodgers the biggest regular-season underdog of his career. The Rams won the game but failed to cover after Todd Gurley went down inside the 10-yard line.)

San Francisco only one loss away from the under

Far away from the success of the Chiefs and Rams are the 49ers, who are one loss away from becoming the first NFL team this season to go under their win total (O/U 8.5). The 49ers lost quarterback Jimmy Garoppolo to a torn ACL in Week 3 -- at Kansas City, no less -- and are 2-7 headed into a Week 10 clash with the New York Giants on Monday night.

The Green Bay Packers (3-4-1, O/U 10), Oakland Raiders (1-7, O/U 7.5) and Philadelphia Eagles (4-4, O/U 10.5) are each two losses away from booking the under. If Green Bay loses at least two more games, it will mark the sixth time they've gone under in the last seven seasons. Bettors who backed the Packers to hit the over this year need them to win out.

Like the Chiefs, the 49ers, Packers, Raiders and Eagles are safe from the over/under record books, even if they were to lose all of their remaining games. The "biggest under" since 2002 came by way of the 2013 Houston Texans (2-14, O/U 10.5), who finished 8.5 wins shy of their total.

Major Super Bowl odds movement

Though 20/20 hindsight may trick you into believing that you saw it all coming, the Chiefs are one of the biggest surprises from an odds perspective this season. Kansas City came into Week 1 at 15-1 to win the AFC and 30-1 to win the Super Bowl, tied for just the 13th best odds in the league. They're now favored to win the conference (+175) and have the third-best odds to hoist the Lombardi Trophy (+450), behind the Rams (+250) and Saints (+350).

Todd Gurley's decision to stop short of the end zone and allow himself to be tackled -- thus ensuring the Rams (-7.5) could run out the clock on their 29-27 win over the Packers -- had fantasy football implications and drew a mixed reaction in Vegas.

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The probability that the Chiefs will win the AFC or Super Bowl, as implied by their odds, has increased more than five-fold since before Week 1. The Rams and Saints, who both began the season at 10-1, have seen their implied probabilities triple and double, respectively. Those increases are meaningful, but because the Rams and Saints started off with better odds than the Chiefs, their moves are not as significant as Kansas City's.

The Chiefs, Rams and Saints are among only eight teams whose Super Bowl odds have compressed (or implied probabilities to win it all have increased) since the season began. They're joined by the Bears (60-1 to 40-1), Bengals (80-1 to 60-1), Steelers (10-1 to 8-1), Carolina Panthers (30-1 to 25-1) and Washington Redskins (100-1 to 80-1).

The biggest downfalls, meanwhile, have come out of the Bay Area. The 49ers and Oakland Raiders were each 40-1 to win the Super Bowl heading into Week 1, very much in the middle of the pack. They are now 10,000-1, worst in the NFL, right alongside the rookie quarterback-led Cardinals, Buffalo Bills and Cleveland Browns.

First-half betting trends

Through Week 9, the Dolphins, Panthers and Patriots are 4-1 ATS at home, best in the NFL. The Chiefs and Saints are both undefeated ATS on the road. The Raiders are a league-worst 2-6 ATS overall.

The Tampa Bay Buccaneers have been the NFL's most "over friendly" team this season, with an over record of 7-1, including a 5-0 mark on the road. The Atlanta Falcons are next at 6-2. The Seahawks have been the most kind to under bettors, going below the point total in six of their eight games.

The NFC East has served up a variety of interesting home and away splits. The Giants are 0-4 ATS at home, but 3-1 ATS on the road. The Eagles have an over record of 0-4 at home and 3-1 on the road. The Cowboys have an over record of 3-1 at home and 0-4 on the road.

NFL teams are scoring at a record clip of 48.1 combined points per game, but sportsbooks have kept pace with the trend, and over/under parity has been maintained. According to TeamRankings.com, 66 games have gone over their point total, 67 have gone under, and there's been one push.